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Oracle LVM mirror split backup

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Thomas Lee_1

Oracle LVM mirror split backup

I have a server running 11.00 and MirrorDisk/UX

As the EOD (End of Day) job grow longer and longer, now finding a way to shorten the backup time.

I'm using Oracle 8i

For backup, I would like to do the followings.
Suppose I use LVM mirror

1. Shutdown the DB
2. Split Mirror
3. Start DB
4. Backup mirror to tape
5. Merge Mirror

Did above step correct? If so, can anyone of
you guru can suggest some script for me?

Or anyother solution? As my DB is running on VA7100, if use LVM mirror, will quite waste storage. But seems using split mirror is a
good way to shortage the backup time to provide
more space for the cron jobs.

Michael Tully
Honored Contributor

Re: Oracle LVM mirror split backup

I don't have a script to do this, but your procedure is seems to be correct.

Shutdown your database
Split the mirror using 'lvsplit' for each logical volume.
Start your database
Backup from the mirror to tape
Run 'lvmerge' to reinstate the mirror.

For some scripting ideas, have a look here:,,0xaa88107d277ad611abdb0090277a778c,00.html

Anyone for a Mutiny ?
Honored Contributor

Re: Oracle LVM mirror split backup


If you run in archive log mode, it is preferable to do HOT backups (never ever shutdown) using RMAN!

You should have ALWAYS been doing hot backups. Split mirrors, unless you have triple mirroring, will open you up to failure during your backup and re-silvering window.

there are many benefits and features in RMAN.

hope this helps!
No person was ever honoured for what he received. Honour has been the reward for what he gave (clavin coolidge)
Sunil Sharma_1
Honored Contributor

Re: Oracle LVM mirror split backup


Your steps are seems to be correct, but by doing this you r adding a single point of failure in system. Suppose during your backup if production disk goes bad you will loose your data.

Best way is to use RMAN backup with archive mode.It takes less time and more accurate.

*** Dream as if you'll live forever. Live as if you'll die today ***
Occasional Advisor

Re: Oracle LVM mirror split backup

Small modifcation in ur order sequence like,

1.Shutdown DB
2.Split mirror
3.Start DB
4.Perform vgchid on all miror copy PVs.
6.Mount and perofrm ur backup activity
7.Recreate the mirror thru lvextend

U can try even by changing all oracle table space to offline mode then perform the above steps from 2 to 7.

But if you have 1+2 mirror copies then all is fine other wise u may open a window for SPOF.

doug mielke
Respected Contributor

Re: Oracle LVM mirror split backup

Hot Backups rock!

After a series of DBA's who told us Oracle Hot backups are un reliable, we finally found one that knew how to run them.

Ours take about 6 hours overnight ( 150 gig dbase) over a 100 mg lan to a NAS filer.
Our system is running at about half capacity during that time. We run these daily, as opposed to the prior plan of weekly shutdown pain.

We test the backups monthly, when we refresh ( recreate) our user test instances, and every other time we build a dev instance. It works so much better than the export / import method.

Thomas Lee_1

Re: Oracle LVM mirror split backup

Oh, if want to prevent SPOF, so double mirror and RMAN can solve..

So, can you guys give me some idea for RMAN?
Honored Contributor

Re: Oracle LVM mirror split backup

A. Clay Stephenson
Acclaimed Contributor

Re: Oracle LVM mirror split backup

There is another solution which you might consider which does not lose redundancy and uses only a small fraction (typically less than 10%) of extra disk. You should look into OnlineJFS snapshot mounts -- they will do what you are trying to do without losing the mirror.

There are a few cases where hotbackups are of limited value. Consider the case of metadata which describe the actual data stored in a database. Unless the application metadata exactly matches the described data then a 'hot' backup, no matter how reliable, is useless. In those pathological cases, you do have to shutdown the database and the applications; snapshot; restart the database and application; and finally backup using the snapshots. This is usually accomplished with only a few minutes of downtime and you then get all the "warm-fuzzy" of a truly cold backup with almost all of the uptime of a hotbackup.
If it ain't broke, I can fix that.
Brian Crabtree
Honored Contributor

Re: Oracle LVM mirror split backup

Our normal for this is:

1. Put database in backup mode
2. Split mirrors
3. Take database out of backup mode
4. Backup mirror to tape
5. Sync mirror

We do not normally shutdown the database. The tablespaces have to be placed in backup mode individually (alter tablespace ... begin backup;) and removed individually (...end backup;). RMAN is a good solution, but can have complications on restores. Generally, this is a good way to backup, and makes restoring easy.

However, you have to make sure that you are getting good copies of the archivelogs every day, as these will be required for the database to be recovered.